It's true, only one button press at a time, no way around it. So it makes real gaming completely impossible, and makes the sideways remote with A and B buttons just a big joke as even NES style games can't be played. But some sorts of games can work, more slow paced stuff for one thing. But a scrolling shooter is definitely out, as you can't even move around properly since rocking the "d-pad" across diagonal won't register the second direction press - you have to distinctly let go of "left" before pressing "up" for it to work.
I'm just talking out loud to get a grasp on if it is truly the remote or if a firmware upgrade to the Roku device could fix it.
I have been considering ways to make my game playable with only tapping buttons and not holding them, although it wouldn't hardly be a scrolling shooter anymore and would move in to some sort of other genre. Regardless it could still be fun.
I wanted to make the Roku version much simpler and completely free. But alas, the roadblocks are in place.